1. Field of the Invention
This invention relates to a sheet delivery mechanism in an image forming apparatus such as a printer, copier or facsimile and a fixing device and the image forming apparatus having the sheet discharging mechanism.
2. Background Art
In the image forming apparatus, it is known that when a sheet with an image formed by an image forming section is delivered or discharged into an output tray, a paper delivery roll pair consisting of a follower roll and pinch roll which sandwich a nip are used.
Until now, a sheet delivery mechanism is known which is a sheet delivery roll serving as an inverting roll for both-side printing, provided with a slope on the side acting when the convex portion of the kicking shape of a pinch roll is inverted (JP-B-7-17295). Another paper delivery mechanism is known in which the rising angle of the convex of the kicking shape on the side acting in delivery is set at 45° or less (JP-A-11-79514). Still another paper delivery has been disclosed in which an elastic blade-like convex is provided so that in sheet feeding the convex is deformed inward in a radial direction and in kicking-out, the convex is acted on the sheet (JP-A-08-246034).
However, if the sheet is discharged with the rear end slanted downward in a certain degree according to the convex in the kicking shape, the sheet interferes with the convex on the downstream side in a rotating direction and floats. Thus, the rear end of the sheet cannot be pushed by the portion of the kicking shape. This led to a problem of poor accommodation due to the leaving the rear end of the sheet.
Further, in order to prevent damage when a thick sheet passes through a nip and poor rotation, it is necessary to reduce the height of the convexes attached to the pinch roll. This requires the performance of kicking out the sheet rear end to be lowered. When the sheet climbs over the convex, this influences the roll nip to generate bending of the sheet. Further, in the case of the elastic blade-like convex, if a fixing roll is arranged in the vicinity of the delivery roll, time-passage deformation was inevitable which is attributable to degradation of the material due to heat or the like.